Corrosion inhibited fluids



CORROSION INHIBITED FLUIDS Robert S. Montgomery, Midland, Mich., assignor to The teat which tend to be extremely corrosive to most of the metals that are commonly employed in such systems.

The coal acids that are employed to prepare the esters utilized in the present invention may be identical with Dow chemical Company, Midland Mich a carport 5 or similar to those which may be obtained in a known mm of Delaware manner bythe oxidation with gaseous oxygen of an aqueous alkaline slurry of a finely divided carbonaceous N0 Dl'aWlhg- Application December 5, 1956 material selected from the group consisting of coal and Serial No. 626,281 coke that has been obtained by the carbonization of coal at temperatures beneath about 700 C. Coal acids that 7 Claims. (Cl. 652.5) have been obtained by the nitric acid oxidation of suit- Thlfi invention relates to and has Its P P able carbonaceous materials are also generally satisfacjective the provision of certain media comprised of base tory fluids consisting of halogenated hydrocarbons that are The f coal aeids are hygroscopic, usually ll i not corrosive -va metal Surfaces, Particularly iron essentially water-soluble material. They are believed and Steel Surfaces, and Which are especially "tile t to be comprised substantially of various aromatic polyemploymeht as hydraulic fluids, as Coolants in metal carboxylic acids in a mixture having an average molecheat-exchanging Systems and for ike purposesular weight in the neighborhood of 250. Their average According to the present invention, a non-cerrodent equivalent weight is generally about eighty. They ordimedium is COl'IlPI'lSfld Of a base fluid 0f the indicated type narily appear to have an average of two and one-half containing a minor proportion of a miscible alkyl ester to five carboxylic groups per molecule with an apparent of coal acids in which the alkyl radical contains less than average f th t four being common. While their about twenty and Preferably from about Seven t0 thirteen exact chemical nature and constitution may be somewhat Car on at s i ts S r ctu e Adyantageollsly, the base conjectural, they evidently contain considerable quantifluid may be rendered non-corrosive to metals to provide i f t id tetra-carboxylic benzene a id as well as 8 ed in accordance With the invention y orporataromatic acids having more complex nuclei. Frequently, ing therein between about 0.01 and 5 percent by Weight of f example, the greatly preponderant proportion of arothe y ester of cDal acids, based on the Weight f the matic nuclei obtained in the conventionally manufactured noll-eoll'odent meflillmy P p it y e coal acids may be found to consist of methylnaphthalene, more advantageous to p y from t0 2 Percent y benzene, biphenyl, naphthalene, phenanthrene, alkyl benweight of the alkyl ester of coal acids in the medium. zene, benzophenone and toluene nuclei.

It is desirable for the alkyl ester of coal acids that is To alford additional delineation, several alkyl esters p y to he a completely of ntially compl t ly of coal acids were tested for their efiicacy in inhibiting the esterlfied p such an ester y be ed r adily corrosiveness upon metals of hexachlorotetrafluorobutane. as the Product of the reaction of tree e081 acids With In testing the halogenated hydrocarbon, about one persuitable alcohols and in other ways analogous to those cent by weight proportions of each of the alkyl esters of in which ordinary polycarboxylic acids are conventionally coal acids that were tested were incorporated in the base esterified. As indicated, it is of particular benefit in fluid. About seventy-five gram portions of each of the some cases for at least about a seven carbon atom alkyl thus-inhibited base fluids were added to a scalable sixradical to be employed in the ester. Esters of this variety ounce glass container along with about twenty-five grams tend to be more readily miscible with a larger proportion of distilled water. A one-quarter by two and one-half of the base fluids that are contemplated as being Within inch strip, having a thickness of about three-sixty-fourths the scope of the invention. Typical of the esters which of an inch, of Formula 52-100 cold rolled steel, wrapped may advantageously be utilized in the practice of the crosswise with seven turns and lengthwise with one turn invention are the isooctyl; 2-ethyl-n-hexyl; decyl; lauryl; of No. 19 copper wire, was inserted in each of the contridecyl and oleyl esters of coal acids and the like as well tainers. The containers were then tightly sealed and as their mixtures. tumbled for about forty-eight hours at a temperature of As mentioned, the base fluids that may be rendered about 200 F. At the termination of this period, the non-corrosive by the alkyl esters of coal acids consist of copper and steel specimens from each of the bottles were liquid halogenated hydrocarbons, including fluorinated, examined closely for evidences of corrosion and the steel chlorinated, brominated and mixed-halogenated derivastrip checked for possible weight loss. Each of the cor tives exclusive of iodine-containing compounds. Pracrosion-inhibited fluids were analyzed for possible changes tice of the invention is exceptionally advantageous with in their viscosity and increases in acidity. The results certain chlorofluorocarbons such as hexachlorotetrafluorowhich were obtained in each of the tests that was butane (C Cl F and the like which are exceptionally conducted are set forth in the following tabulation which useful as hydraulic fluids (as, for example, in the hyalso includes certain of the physical properties of the draulic operating systems for airplane landing gear) but particular esters that were utilized for testing purposes.

Corrosion- Oorrosion- Viscosity Viscosity Viscosity Pour Specific Inhibiting iblting of Esterin of Ester in Index of Point of Gravity Properties Ester of centipoises centipoises Ester Esterln of Ester In'lest Coal Acids at F. at 210 0.- F. at 25l25 C With 4CleF4 Isooctyl 629 30. 05 76 0 Excellent. Z-Ethyl-n-hcxyL 695 32. 45 78 -5 Do. De 96 12.16 -20 0.963 Do.

195 20.23 119 +35 0. 955 Good. 900 37.23 16 +10 0. 973 Do. 83. 76 13. 50 +25 Do.

As determined by A.8.T.M. D-445-53T for viscosity and D-567-53 l'or viscosity index. As determined by A.S.T.M. D-97-47.

Not determined.

Inicomparisomtests conducted with uninhibited control' samples caused extreme corrosion .of the metal specimens None of the infrom the halogenated hydrocarbon.

that were hibited hexachlorotetrafluorobutane fluids :testcd showed any appreciable change in viscosity or acid number after the tests. Likewise, no appreciable weight loss was discernible in the metal specimens tested in the than about twenty carbon atoms in its structure; said coal acids being the water soluble mixed aromatic polycarboxylic'acids that are the products of the oxidation of coal and the like carbonaceous materials, which acids typicallyshave an average molecular weight of about 250,

anaverage apparent equivalent weight of about 80, and

contain an average of from about two and oneshalf to 'five carboxylic groups per aromatic nuclei in their molecule.

2. The composition of claim 1 containing from about 0.1 to 2 percent by weight of the dispersed ester.

3. Non-corrodent composition comprised of 21 normally liquid chlorofiuorocarbon fluid in which there is dispersed between about 0.01 and, 5 percent by weight of an alkyl ester of coal acids in which the alkyl radical contains from about seven to thirteen carbon atoms.

4. The composition of claim 3, wherein the ester is the isoocytl ester of coal acids.

5. The composition of claim 3, wherein the ester is the Z-ethyl-n-hexyl ester of coal acids.

6. The composition of claim 3, wherein the ester is the decyl ester of coal acids.

7. The composition of claim 3, wherein the chlorofluorocarbon fluid is hexachlorotetrafluorobutane.

References Cited in the file of this patent UNITED STATES PATENTS 2,516,640 Montgomery et al. July '25, 1950 

1. NON-CORRODENT COMPOSITION COMPRISED OF A BASE FLUID CONSISTING OF A NORMALLY LIQUID HALOGENATED HYDROCARBON IN WHICH THERE IS DISPERSED A MINOR PROPORTION THAT IS NOT IN EXCESS OF ABOUT 5 PERCENT BY WEIGHT, BASED ON THE WEIGHT OF SAID COMPOSITION, OF A MISCIBLE ALKYL ESTER OF COAL ACIDS IN WHICH THE ALKYL RADICAL CONTAINS LESS THAN ABOUT TWENTY CARBON ATOMS IN ITS STRUCTURE; SAID COAL ACIDS BEING THE WATER SOLUBLE MIXED AROMATIC POLYCARBOXYLIC ACIDS THAT ARE THE PRODUCTS OF THE OXIDATION OF COAL AND THE LIKE CARBONACEOUS MATERIALS, WHICH ACIDS TYPICALLY HAVE AN AVERAGE MOLECULAR WEIGHT OF ABOUT 250, AN AVERAGE APPARENT EQUIVALENT WEIGHT OF ABOUT 80, AND CONTAIN AN AVERAGE OF FROM ABOUT TWO AND ONE-HALF TO FIVE CARBOXYLIC GROUPS PER AROMATIC NUCLEI IN THEIR MOLECULE. 